Two ways to judge whether a JS object has a certain attribute _javascript skill

Two ways, but slightly different

1,in operator

Copy Code code as follows:

var obj = {name: ' Jack '};
Alert (' name ' in obj); --> true
Alert (' toString ' in obj); --> true

You can see that the return true is detected either by name or by ToString on the prototype chain.

2,hasownproperty method

Copy Code code as follows:

var obj = {name: ' Jack '};
Obj.hasownproperty (' name '); --> true
Obj.hasownproperty (' toString '); --> false

The inherited attribute on the prototype chain could not be detected by hasOwnProperty and returns false.

It should be noted that although in can detect the properties of the prototype chain, for-in is usually not.

Of course, after the prototype is rewritten, for-in is visible under Ie9/firefox/safari/chrome/opera. See: For the flaw in